The most common type of lid construction for soft drink or beer cans, is the pull-ring type in which a pull ring is secured to a removable closure or tab which normally encloses the pouring opening in the lid. By initially pivoting the ring from a horizontal position to a position generally normal to the lid, the seal will be broken to vent the pressure from the can and continued upward pulling on the ring will tear the tab from the opening. Problems have arisen in the past in that the pull ring and tab are usually discarded. Discarding of the tabs not only provides a substantial amount of litter, but also provides a hazard in that the tabs have sharp edges and cause lacerations to feet or clothing. Because of the litter problems associated with the pull tabs, legislation has been passed in certain areas of the country prohibiting the sale of cans with pull tabs.
To avoid the disadvantages of the pull tab, attempts have been made to utilize a push tab, in which the tab is pushed inwardly into the can in order to open the pouring opening. In one form of push-tab arrangement, a single hole or opening is formed in the lid of the can which is enclosed by a tab or closure. The tab can either be cut or scored through the lid with the joint sealed on the inside by a suitable adhesive or sealant, or alternately, the tab can be partially scored, in which case no internal sealant is required. As the cans usually contain either a carbonated soft drink or beer, there is a substantial internal pressure and due to the size of the pouring opening, it is very difficult to depress the tab against the internal pressure exerted by the beverage. A further disadvantage of the push-tab as used in the past is that the finger of the consumer may be pushed downwardly into the can when the tab is depressed, contacting the rough edge bordering the opening which may cause lacerations to the finger.
To facilitate opening of a push-tab attempts have been made to utilize a pair of openings in the lid of the can, one being a larger pouring hole and the second being a small vent hole. With this type of construction, the vent-tab is initially depressed to vent the internal pressure. With the internal pressure vented, the larger pouring tab can then be easily depressed to open the pouring hole. This type of construction has disadvantages in that the consumer must be educated as to the manner of opening the can, meaning that special instructions must be imprinted or embossed on the can lid indicating that the vent tab should be initially opened. As a further disadvantage, the pouring hole, in this type of construction, is often located a substantial distance from the edge of the can, making the can difficult from which to drink or pour.